Heck yeah you can! The sour part of sour gummies comes from citric acid (also known as ascorbic acid). If you already do home canning, you likely already have some in your pantry. I have found that the best results for making sour CBD gummies requires that you pulse the citric acid powder in a spice grinder or food processor until quite fine. Once the gummies have just set up, pop them out of their molds and toss them with citric acid to dust them. The longer the gummies set, the more dry their exterior becomes, making it harder to get the citric acid to adhere. Also note that the citric acid can interfere with the gelatin, so you might want to keep your sour CBD gummies in the fridge ~or~ add another 1/2 Tbsp of gelatin to the mix to prevent them from melting into one big blob.