If you find yourself without instant vanilla pudding mix, there are a few substitutes you can use. One option is to mix 1 cup of heavy cream with 1/4 cup of sugar. Whip the cream and sugar together until stiff peaks form, then fold them into your recipe. Another option is to use a homemade vanilla custard, made with milk, sugar, eggs, and vanilla extract. Simply cook the ingredients together on the stove until thickened, then let them cool before using them in your recipe.