The best replacement for sodium bicarbonate is sodium carbonate.

The best alternatives to sodium bicarbonate are rated as following:
★★★★★  sodium carbonate
★★★★  baking soda
★★★  sodium chloride
★★  calcium carbonate
★★  soda ash
★★  sodium citrate
★★  sodium hydroxide
★★  potassium bicarbonate
★  bicarbonate of soda
★  sodium hydrogen carbonate
★  sodium phosphate
  ammonium bicarbonate
  normal saline
  sodium percarbonate
  sodium acetate
  natrium bicarbonate
  calcium bicarbonate
  potassium citrate
  magnesium hydroxide

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Speaking about sodium bicarbonate, one probably shouldn't forget about citric acid.

Other search terms related to sodium bicarbonate and their ratings are:

★★★★★ citric acid
★★★★★ acetic acid
★★★★ acid
★★★★ lidocaine
★★★ sulfuric acid
★★★ hydrochloric acid
★★★ magnesium chloride
★★ carboxylic acid
benzoic acid
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Google Trends

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sodium bicarbonate
sodium carbonate
baking soda