Spillable var instead of checking for OPENCONTAINER as that flag encompasses a lot more than necessary.

code/modules/food&drinks/drinks/drinks.dm

@@ -112,6 +112,7 @@
 	possible_transfer_amounts = null
 	volume = 150
 	flags = CONDUCT | OPENCONTAINER
+	spillable = 1
 
 /obj/item/weapon/reagent_containers/food/drinks/golden_cup/tournament_26_06_2011
 	desc = "A golden cup. It will be presented to a winner of tournament 26 june and name of the winner will be graved on it."
@@ -127,6 +128,7 @@
 	desc = "Careful, the beverage you're about to enjoy is extremely hot."
 	icon_state = "coffee"
 	list_reagents = list("coffee" = 30)
+	spillable = 1
 
 /obj/item/weapon/reagent_containers/food/drinks/tea
 	name = "Duke Purple Tea"
@@ -134,12 +136,14 @@
 	icon_state = "tea"
 	item_state = "coffee"
 	list_reagents = list("tea" = 30)
+	spillable = 1
 
 /obj/item/weapon/reagent_containers/food/drinks/ice
 	name = "Ice Cup"
 	desc = "Careful, cold ice, do not chew."
 	icon_state = "coffee"
 	list_reagents = list("ice" = 30)
+	spillable = 1
 
 /obj/item/weapon/reagent_containers/food/drinks/h_chocolate
 	name = "Dutch Hot Coco"
@@ -147,6 +151,7 @@
 	icon_state = "tea"
 	item_state = "coffee"
 	list_reagents = list("hot_coco" = 30, "sugar" = 5)
+	spillable = 1
 
 /obj/item/weapon/reagent_containers/food/drinks/dry_ramen
 	name = "Cup Ramen"
@@ -173,6 +178,7 @@
 	icon_state = "water_cup_e"
 	possible_transfer_amounts = null
 	volume = 10
+	spillable = 1
 
 /obj/item/weapon/reagent_containers/food/drinks/sillycup/on_reagent_change()
 	if(reagents.total_volume)
@@ -211,6 +217,7 @@
 	desc = "A cup with the british flag emblazoned on it."
 	icon_state = "britcup"
 	volume = 30
+	spillable = 1
 
 //////////////////////////soda_cans//
 //These are in their own group to be used as IED's in /obj/item/weapon/grenade/ghettobomb.dm

code/modules/food&drinks/drinks/drinks/drinkingglass.dm

@@ -8,6 +8,7 @@
 	volume = 50
 	burn_state = 0 //Burnable
 	burntime = 5
+	spillable = 1
 
 /obj/item/weapon/reagent_containers/food/drinks/drinkingglass/fire_act()
 	if(!reagents.total_volume)

code/modules/reagents/reagent_containers.dm

@@ -10,6 +10,7 @@
 	var/list/list_reagents = null
 	var/spawned_disease = null
 	var/disease_amount = 20
+	var/spillable = 0
 
 /obj/item/weapon/reagent_containers/verb/set_APTFT() //set amount_per_transfer_from_this
 	set name = "Set transfer amount"
@@ -81,7 +82,7 @@
 /obj/item/weapon/reagent_containers/throw_impact(atom/target,mob/thrower)
 	..()
 
-	if(!reagents.total_volume || !is_open_container())
+	if(!reagents.total_volume || !spillable)
 		return
 
 	if(ismob(target) && target.reagents)

code/modules/reagents/reagent_containers/glass.dm

@@ -4,6 +4,7 @@
 	possible_transfer_amounts = list(5, 10, 15, 25, 30, 50)
 	volume = 50
 	flags = OPENCONTAINER
+	spillable = 1
 
 	can_be_placed_into = list(
 		/obj/machinery/chem_master/,