Does inhaling glue (glue sniffing) reduce appetite?
Short answer
Various inhalants, most notably organic solvents including those used in paint and glue suppress appetite.

Background
From the Division of Alcohol and Drug Abuse I learned the following: 


  Initial effects [of various inhalants] include nausea [...], and a loss of appetite. 


And the Humanitarian Irin News reports the following on Nepali street youths: 


  The adhesive glue contains toluene, [an] intoxicating hydrocarbon [...]. The solvent [...] causes hallucinations as well as dampening hunger pangs [...].


Indeed, acute exposure to organic solvents has been associated with a loss of appetite (Gregerson, 1998), and chronic exposure to toluene in the industrial workforce has also been linked to appetite suppression (Kishi et al., 1993).         

References
- Gregerson, Am J Industr Med (1998); 14(6): 681–701
- Kishi et al., Environmental Res (1993); 62(2): 303–13