I have some food coloring gel that seems way too thick, like it dried out just a little.  What is the best thing to add to thin it out?  I'm just adding it to cake batter.  I was going to use regular food coloring but I don't have the right color on hand.  I wasn't sure if water was okay or if needed to be alcohol based.

ASometimes I have success using slightly dried out gel colour, especially if you can scrape away the surface skin and use better stuff underneath. Sometimes, though, it just won't incorporate and forms clumps of colour in the icing etc I'm trying to use it in. Maybe try a little bit in a spoonful of the batter and see if it mixes, then you're not wasting the whole lot if it doesn't work. But if it's for a paying customer and it's out of date, then don't even think about it.

AI think I've read that you can add glycerin but I've never done it myself

AIf you use it in the batter, just mix it with the liquid you add anyway, f.e. milk, vanilla essence or even eggs. If you need it later to paint on details, mix it with a little vodka or extract (f.e. lemon,almond or vanilla).

AIf you use it in the batter, just mix it with the liquid you add anyway, f.e. milk, vanilla essence or even eggs. If you need it later to paint on details, mix it with a little vodka or extract (f.e. lemon,almond or vanilla).