My sensory bag was inspired by Plain Vanilla Mom but she used hair gel in her bag, and let's be honest here, I don't even dry my hair let alone put product in it, so I didn't have any hair gel laying around the house. I did have dish soap, though, and that is what I used. All you need is a gallon-sized Ziploc bag, some duct tape, dish soap, and little trinkets you can put inside the bag. Everything I used I had in my house.
I first duct taped the sides of the bag. Next, I dumped in the dish soap. I used about 1/3 of the bottle shown here. Then I scrounged up as many little trinkets I could find. We had just cleaned the play room the day before, or else I probably wouldn't have had to look so hard! I ended up putting in some plastic easter grass, a nickel, a penny, a square of bubble wrap, some plastic paper clips, some water beads, and (my favorite!) some glitter. After adding everything inside the bag, I zipped it and sealed it with two layers of duct tape.
Finally, I let baby girl have at it! She loved it! I had to show her what to do at first, but she loved smushing the dish soap around and feeling all of the different textures. She had to be very closely supervised, though, because she does still enjoy putting everything in her mouth. Those two teeth she has are very sharp and I didn't want her to puncture the bag. A happy accident that occurred since I used dish soap is the more she played with it, it started to form bubbles. That was fun for her (and my five-year-old) to see.