Picked this soda bottle up last week , not sure what it is that is caked inside in places . Some of it is kind of gummy and sticky as well as some of it being dry and quite hard and stuck to the glass in places . I got a little bit of it out where it was thin . Tried sand and water and shook it for quite a while , did not budge it . Tried scraping it off where I could get to it with a scew driver and some of it is caked on the glass and is very hard . Tried vinegar and baking soda with no luck . Any suggestions as to what to put in it that would soften this substance up to be able to remove it . Adding some pics but it was hard to get a good picture of it .