You can join some food dispensing toys together to make the toys more difficult.
For example a Classic Kong toy (size L) and a Kong Traxx toy (size M/L) can be joined together. Just put some of your dog’s favourite treats inside the Traxx toy and then push the Classic Kong throught the tire. It usually takes Miki about 2-10 minutes to pull the Classic Kong toy out of the Traxx.
You can join a Kong Traxx toy (size M/L) with a Busy Buddy Twist’n Treat toy (size L). Just twist the Busy Buddy open and put the Traxx on top of the other half. Then add some small treats or just kibble and twist the Busy Buddy loosely together. It tool Miki about 4 minutes to get the kibble out of this.
I’ve also combined the Kong Traxx toy (size M/L) with a JW Playbites Caterpillar toy (size L). I put these relatively large Nutrivet Instinct Dog Treats and some kibble inside the tire and then I pushed the Caterpillar through the tire. It took Miki about 2-3 minutes to get the treats out.
Kong Company says that the Kong Genius –toys are also connectable. Just stick a Kong Genius Leo into a Kong Genius Mike or stick multiple Leos together.